PSI - Issue 45

Ali et al. / Structural Integrity Procedia 00 (2023) 000 – 000

Zulfiqar Ali et al. / Procedia Structural Integrity 45 (2023) 60 – 65

64

Modified TMM

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 Felicity Ratio (FR)

Coal

Limestone

Sandstone

Granite

Bluestone

1 Week

6 Hrs 72 Hrs

1 Hrs

No delay 0.5 Hrs

Time Delay

Fig. 5. Scatter plot showing FR for the rock specimens measured using Modified TMM at various time delays.

4. Conclusion In this study we investigated the influence of time delay on the stress memory in rocks using the TMM method. Our findings suggest that the TMM method is effective within a specific range of time delays. However, for larger time delays exceeding 24 hours, the results are sensitive to the duration of the delay, making the TMM method impractical for in-situ stress measurement. Our study revealed that stress relaxation and hysteresis loop are the main factors contributing to this discrepancy. To overcome this limitation, we proposed a modified method based on gradient change function, which was found to be reliable and consistent in measuring applied stresses. Our study demonstrates that the sensitivity of rock stress memory to time is not an inherent material property, instead it is associated with the methodology applied to study it. The results from our proposed method are comparable with other techniques like DRA and AE on preloaded specimens, however, further research is required to explore its potential use for in-situ stress measurement from oriented cored rocks. Acknowledgements The authors are grateful to the Australia Coal Industry’s research Program (ACARP) for funding this research under project C29010. References Ali, Z, Karakus, M, Nguyen, G D, Amrouch, K 2022, ‘ Effect of loading rate and time delay on the tangent modulus method in coal and coal measured rocks ’ , International Journal of Coal Science and Technology , vol. 9, no. 81. https://doi: 10.1007/s40789-022-00552-7 Ali, Z, Karakus, M, Nguyen, G D, Amrouch, K 2022, ‘ Application of full-field strain measurement to study the Kaiser effect in granite under indirect tensile loading ’, Proceedings of the 56th US Rock mechanics / Geomechanics Symposium . Santa Fe: American Rock Mechanics Association. [google scholar] Ali, Z, Karakus, M, Nguyen, G D, Amrouch, K 2021, ‘Understanding the Kaiser effect in concrete using deformation rate analysis and acoustic emission’, Proceedings of the 10th Australasian Conference on Applied Mechanics . Adelaide: Engineers Australia. [google scholar] Karakus, M, Perez, S, Goodchild, D 2015, ‘In -situ Stress Measurement from Oriented Sub-cores Using Kaiser Ef fect’, Proceedings of the 24th International Mining Congress and Exhibition of Turkey . Antalya: Chamber of Mining Engineers of Turkey. [google scholar] Fujii, Y, Makasib, M, Kodamaa, J, Fukudaa, D, Gotoc, K, Kumakurac, S, Kanaokad, M 2018, ‘ Tangent modulus method – an original method to measure in-situ rock stress ’, Tunneling and Underground Space Technology , vol. 82, pp. 148 – 155. [cross reference] Lavrov, A 2003, ‘ The KE in rocks: principles and stress estimation techniques ’, International Journal of Rock Mechanics and Mining Sciences , vol.40, no.2, pp. 151 – 171. https://doi.org/10.1016/S1365-1609(02)00138-7 Ban, Y, Fu, X, Xie, Q, Duan, J 2020, ‘ Time-sensitivity mechanism of rock stress memory properties under tensile stress ’, Journal of Rock Mechanics and Geotechnical Engineering, vol. 12, pp. 528-540. https://doi.org/10.1016/j.jrmge.2019.12.012 Fairhurst, C, E, Hudson, J, A 1999, ‘ Draft ISRM suggested method for the complete stress-strain curve for intact rock in uniaxial compression ’, International Journal of Rock Mechanics and Mining Sciences , vol. 36, pp. 281-289.